Eight police officers have been killed in an ambush in northern Mexico.

An official at the Sinaloa state attorney general's office says gunmen attacked four police cars on a highway in the town of Navolato on Monday. A ninth officer was wounded.

The official says the gunmen fled, although police found a vehicle several miles (kilometers) from the site that may have belonged to the attackers. The official spoke on condition of anonymity because of security reasons.

Sinaloa is the cradle of a powerful cartel by the same name.

Meanwhile, in the border city of Tijuana, police found the decapitated bodies of two men hung by their feet off a bridge. Their heads were found in a car abandoned on the bridge.